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diff --git a/tex/src/appendix-existing-tools.tex b/tex/src/appendix-existing-tools.tex index d923d5f..1d0b383 100644 --- a/tex/src/appendix-existing-tools.tex +++ b/tex/src/appendix-existing-tools.tex @@ -47,11 +47,11 @@ VMs thus provide the ultimate control one can have over the run-time environment However, the VM's kernel does not talk directly to the running hardware that is doing the analysis, it talks to a simulated hardware layer that is provided by the host's kernel. Therefore, a process that is run inside a virtual machine can be much slower than one that is run on a native kernel. An advantage of VMs is that they are a single file that can be copied from one computer to another, keeping the full environment within them if the format is recognized. -VMs are used by cloud service providers, enabling fully independent operating systems on their large servers (where the customer can have root access). +VMs are used by cloud service providers, enabling fully independent operating systems on their large servers where the customer can have root access. VMs were used in solutions like SHARE \citeappendix{vangorp11} (which was awarded second prize in the Elsevier Executable Paper Grand Challenge of 2011 \citeappendix{gabriel11}), or in suggested reproducible papers like \citeappendix{dolfi14}. However, due to their very large size, these are expensive to maintain, thus leading SHARE to discontinue its services in 2019. -The URL to the VM file \texttt{provenance\_machine.ova} that is mentioned in \citeappendix{dolfi14} is not currently accessible (we suspect that this is due to size and archival costs). +The URL to the VM file \texttt{provenance\_machine.ova} that is mentioned in \citeappendix{dolfi14} is also not currently accessible (we suspect that this is due to size and archival costs). \subsubsection{Containers} \label{appendix:containers} @@ -65,7 +65,7 @@ We review some of the most common container solutions: Docker, Singularity, and \begin{itemize} \item {\bf\small Docker containers:} Docker is one of the most popular tools nowadays for keeping an independent analysis environment. - It is primarily driven by the need of software developers for reproducing a previous environment, where they have root access mostly on the ``cloud'' (which is just a remote VM). + It is primarily driven by the need of software developers for reproducing a previous environment, where they have root access mostly on the ``cloud'' (which is usually a remote VM). A Docker container is composed of independent Docker ``images'' that are built with a \inlinecode{Dockerfile}. It is possible to precisely version/tag the images that are imported (to avoid downloading the latest/different version in a future build). To have a reproducible Docker image, it must be ensured that all the imported Docker images check their dependency tags down to the initial image which contains the C library. @@ -91,16 +91,16 @@ Meng \& Thain \citeappendix{meng17} also give similar reasons on why Docker imag On a more fundamental level, VMs or containers do not store \emph{how} the core environment was built. This information is usually in a third-party repository, and not necessarily inside the container or VM file, making it hard (if not impossible) to track for future users. -This is a major problem when considering reproducibility, which is also highlighted as a major issue in terms of long term reproducibility in \citeappendix{oliveira18}. +This is a major problem in relation to the proposed completeness criteria and is also highlighted as an issue in terms of long term reproducibility by \citeappendix{oliveira18}. -The example of \cite{mesnard20} was previously mentioned in +The example of \inlinecode{Dockerfile} of \cite{mesnard20} was previously mentioned in \ifdefined\separatesupplement the main body of this paper, when discussing the criteria. \else in Section \ref{criteria}. \fi Another useful example is the \href{https://github.com/benmarwick/1989-excavation-report-Madjedbebe/blob/master/Dockerfile}{\inlinecode{Dockerfile}} of \citeappendix{clarkso15} (published in June 2015) which starts with \inlinecode{FROM rocker/verse:3.3.2}. -When we tried to build it (November 2020), the core downloaded image (\inlinecode{rocker/verse:3.3.2}, with image ``digest'' \inlinecode{sha256:c136fb0dbab...}) was created in October 2018 (long after the publication of that paper). +When we tried to build it (November 2020), we noticed that the core downloaded image (\inlinecode{rocker/verse:3.3.2}, with image ``digest'' \inlinecode{sha256:c136fb0dbab...}) was created in October 2018 (long after the publication of that paper). In principle, it is possible to investigate the difference between this new image and the old one that the authors used, but that would require a lot of effort and may not be possible when the changes are not available in a third public repository or not under version control. In Docker, it is possible to retrieve the precise Docker image with its digest, for example, \inlinecode{FROM ubuntu:16.04@sha256:XXXXXXX} (where \inlinecode{XXXXXXX} is the digest, uniquely identifying the core image to be used), but we have not seen this often done in existing examples of ``reproducible'' \inlinecode{Dockerfiles}. @@ -123,7 +123,7 @@ The virtual machine and container solutions mentioned above, have their own inde Another approach to having an isolated analysis environment is to use the same file system as the host, but installing the project's software in a non-standard, project-specific directory that does not interfere with the host. Because the environment in this approach can be built in any custom location on the host, this solution generally does not require root permissions or extra low-level layers like containers or VMs. However, ``moving'' the built product of such solutions from one computer to another is not generally as trivial as containers or VMs. -Examples of such third-party package managers (that are detached from the host OS's package manager) include Nix, GNU Guix, Python's Virtualenv package, and Conda, among others. +Examples of such third-party package managers (that are detached from the host OS's package manager) include (but are not limited to) Nix, GNU Guix, Python's Virtualenv package, Conda. Because it is highly intertwined with the way software is built and installed, third party package managers are described in more detail as part of Section \ref{appendix:packagemanagement}. Maneage (the solution proposed in this paper) also follows a similar approach of building and installing its own software environment within the host's file system, but without depending on it beyond the kernel. @@ -140,7 +140,7 @@ Package management is the process of automating the build and installation of a A package manager thus contains the following information on each software package that can be run automatically: the URL of the software's tarball, the other software that it possibly depends on, and how to configure and build it. Package managers can be tied to specific operating systems at a very low level (like \inlinecode{apt} in Debian-based OSs). Alternatively, there are third-party package managers that can be installed on many OSs. -Both are discussed in more detail in what follows. +Both are discussed in more detail below. Package managers are the second component in any workflow that relies on containers or VMs for an independent environment, and the starting point in others that use the host's file system (as discussed above in Section \ref{appendix:independentenvironment}). In this section, some common package managers are reviewed, in particular those that are most used by the reviewed reproducibility solutions of Appendix \ref{appendix:existingsolutions}. @@ -148,7 +148,7 @@ For a more comprehensive list of existing package managers, see \href{https://en Note that we are not including package managers that are specific to one language, for example \inlinecode{pip} (for Python) or \inlinecode{tlmgr} (for \LaTeX). \subsubsection{Operating system's package manager} -The most commonly used package managers are those of the host operating system, for example, \inlinecode{apt} or \inlinecode{yum} respectively on Debian-based, or RedHat-based GNU/Linux operating systems, \inlinecode{pkg} in FreeBSD, among many others in other OSes. +The most commonly used package managers are those of the host operating system, for example, \inlinecode{apt}, \inlinecode{yum} or \inlinecode{pkg} which are respectively used in Debian-based, Red Hat-based and FreeBSD-based OSs (among many other OSs). These package managers are tightly intertwined with the operating system: they also include the building and updating of the core kernel and the C library. Because they are part of the OS, they also commonly require root permissions. @@ -163,38 +163,44 @@ Hence a fixed version of the dependencies must also be specified. In robust package managers like Debian's \inlinecode{apt} it is possible to fully control (and later reproduce) the built environment of a high-level software. Debian also archives all packaged high-level software in its Snapshot\footnote{\inlinecode{\url{https://snapshot.debian.org/}}} service since 2005 which can be used to build the higher-level software environment on an older OS \citeappendix{aissi20}. -Therefore it is indeed theoretically possible to reproduce the software environment only using archived operating systems and their own package managers, but unfortunately, we have not seen it practiced in scientific papers/projects. +Therefore it is indeed theoretically possible to reproduce the software environment only using archived operating systems and their own package managers, but unfortunately, we have not seen it practiced in (reproducible) scientific papers/projects. -In summary, the host OS package managers are primarily meant for the operating system components or very low-level components. -Hence, many robust reproducible analysis solutions (reviewed in Appendix \ref{appendix:existingsolutions}) do not use the host's package manager, but an independent package manager, like the ones discussed below. +In summary, the host OS package managers are primarily meant for the low-level operating system components. +Hence, many robust reproducible analysis workflows (reviewed in Appendix \ref{appendix:existingsolutions}) do not use the host's package manager, but an independent package manager, like the ones discussed below. -\subsubsection{Packaging with Linux containerization} -Once a software is packaged as an AppImage\footnote{\inlinecode{\url{https://appimage.org}}}, Flatpak\footnote{\inlinecode{\url{https://flatpak.org}}} or Snap\footnote{\inlinecode{\url{https://snapcraft.io}}} the software's binary product and all its dependencies (not including the core C library) are packaged into one file. -This makes it very easy to move that single software's built product to newer systems. -However, because the C library is not included, it can fail on older systems. -Moreover, these are designed for the Linux kernel (using its containerization features) and can thus only be run on GNU/Linux operating systems. +\subsubsection{Blind packaging of already built software} +An already-built software contains links to the system libraries it uses. +Therefore one way of packaging a software is to look into the binary file for the libraries it uses and bring them into a file with the executable so on different systems, the same set of dependencies are moved around with the desired software. +Tools like AppImage\footnote{\inlinecode{\url{https://appimage.org}}}, Flatpak\footnote{\inlinecode{\url{https://flatpak.org}}} or Snap\footnote{\inlinecode{\url{https://snapcraft.io}}} are designed for this purpose: the software's binary product and all its dependencies (not including the core C library) are packaged into one file. +This makes it very easy to move that single software's built product and already built dependencies to different systems. +However, because the C library is not included, it can fail on newer/older systems (depending on the system it was built on). +We call this method ``blind'' packaging because it is agnostic to \emph{how} the software and its dependencies were built (which is important in a scientific context). +Moreover, these types of packagers are designed for the Linux kernel (using its containerization and unique mounting features). +They can therefore only be run on GNU/Linux operating systems. \subsubsection{Nix or GNU Guix} \label{appendix:nixguix} -Nix \citeappendix{dolstra04} and GNU Guix \citeappendix{courtes15} are independent package managers that can be installed and used on GNU/Linux operating systems, and macOS (only for Nix, prior to macOS Catalina). +Nix\footnote{\inlinecode{\url{https://nixos.org}}} \citeappendix{dolstra04} and GNU Guix\footnote{\inlinecode{\url{https://guix.gnu.org}}} \citeappendix{courtes15} are independent package managers that can be installed and used on GNU/Linux operating systems, and macOS (only for Nix, prior to macOS Catalina). Both also have a fully functioning operating system based on their packages: NixOS and ``Guix System''. GNU Guix is based on the same principles of Nix but implemented differently, so we focus the review here on Nix. The Nix approach to package management is unique in that it allows exact dependency tracking of all the dependencies, and allows for multiple versions of software, for more details see \citeappendix{dolstra04}. -In summary, a unique hash is created from all the components that go into the building of the package. +In summary, a unique hash is created from all the components that go into the building of the package (including the instructions on how to build the software). That hash is then prefixed to the software's installation directory. As an example from \citeappendix{dolstra04}: if a certain build of GNU C Library 2.3.2 has a hash of \inlinecode{8d013ea878d0}, then it is installed under \inlinecode{/nix/store/8d013ea878d0-glibc-2.3.2} and all software that is compiled with it (and thus need it to run) will link to this unique address. This allows for multiple versions of the software to co-exist on the system, while keeping an accurate dependency tree. -As mentioned in \citeappendix{courtes15}, one major caveat with using these package managers is that they require a daemon with root privileges. +As mentioned in \citeappendix{courtes15}, one major caveat with using these package managers is that they require a daemon with root privileges (failing our completeness criteria). This is necessary ``to use the Linux kernel container facilities that allow it to isolate build processes and maximize build reproducibility''. This is because the focus in Nix or Guix is to create bit-wise reproducible software binaries and this is necessary for the security or development perspectives. -However, in a non-computer-science analysis (for example natural sciences), the main aim is reproducible \emph{results} that can also be created with the same software version that may not be bit-wise identical (for example when they are installed in other locations, because the installation location is hard-coded in the software binary). +However, in a non-computer-science analysis (for example natural sciences), the main aim is reproducible \emph{results} that can also be created with the same software version that may not be bit-wise identical (for example when they are installed in other locations, because the installation location is hard-coded in the software binary or for a different CPU architecture). -Finally, while Guix and Nix do allow precisely reproducible environments, it requires extra effort. -For example, simply running \inlinecode{guix install gcc} will install the most recent version of GCC that can be different at different times. +Finally, while Guix and Nix do allow precisely reproducible environments, it requires extra effort on the user's side to ensure that the built environment is reproducible later. +For example, simply running \inlinecode{guix install gcc} (the most common way to install a new software) will install the most recent version of GCC, that can be different at different times. Hence, similar to the discussion in host operating system package managers, it is up to the user to ensure that their created environment is recorded properly for reproducibility in the future. -Generally, this is a major limitation of projects that rely on detached package managers for building their software, including the other tools mentioned below. +It is not a complex operation, but like the Docker digest codes mentioned in Appendix \ref{appendix:containers}, many will probably not know, forget or ignore it. +Generally, this is an issue with projects that rely on detached (third party) package managers for building their software, including the other tools mentioned below. +We solved this problem in Maneage by including the package manager and analysis steps into one project: it is simply not possible to forget to record the exact versions of the software used. \subsubsection{Conda/Anaconda} \label{appendix:conda} @@ -206,12 +212,12 @@ However, it is not possible to fix the versions of the dependencies through the This is thoroughly discussed under issue 787 (in May 2019) of \inlinecode{conda-forge}\footnote{\url{https://github.com/conda-forge/conda-forge.github.io/issues/787}}. In that discussion, the authors of \citeappendix{uhse19} report that the half-life of their environment (defined in a YAML file) is 3 months, and that at least one of their dependencies breaks shortly after this period. The main reply they got in the discussion is to build the Conda environment in a container, which is also the suggested solution by \citeappendix{gruning18}. -However, as described in Appendix \ref{appendix:independentenvironment}, containers just hide the reproducibility problem, they do not fix it: containers are not static and need to evolve (i.e., re-built) with the project. +However, as described in Appendix \ref{appendix:independentenvironment}, containers just hide the reproducibility problem, they do not fix it: containers are not static and need to evolve (i.e., get re-built) with the project. Given these limitations, \citeappendix{uhse19} are forced to host their conda-packaged software as tarballs on a separate repository. Conda installs with a shell script that contains a binary-blob (+500 megabytes, embedded in the shell script). This is the first major issue with Conda: from the shell script, it is not clear what is in this binary blob and what it does. -After installing Conda in any location, users can easily activate that environment by loading a special shell script into their shell. +After installing Conda in any location, users can easily activate that environment by loading a special shell script. However, the resulting environment is not fully independent of the host operating system as described below: \begin{itemize} @@ -219,12 +225,12 @@ However, the resulting environment is not fully independent of the host operatin However, the host operating system's directories are also appended afterward. Therefore, a user or script may not notice that the software that is being used is actually coming from the operating system, and not from the controlled Conda installation. -\item Generally, by default, Conda relies heavily on the operating system and does not include core analysis components like \inlinecode{mkdir}, \inlinecode{ls} or \inlinecode{cp}. - Although they are generally the same between different Unix-like operating systems, they have their differences. - For example, \inlinecode{mkdir -p} is a common way to build directories, but this option is only available with GNU Coreutils (default on GNU/Linux systems). - Running the same command within a Conda environment on a macOS would crash. +\item Generally, by default, Conda relies heavily on the operating system and does not include core commands like \inlinecode{mkdir} (to make a directory), \inlinecode{ls} (to list files) or \inlinecode{cp} (to copy). + Although a minimal functionality is defined for them in POSIX and generally behave similarly for basic operations on different Unix-like operating systems, they have their differences. + For example, \inlinecode{mkdir -p} is a common way to build directories, but this option is only available with the \inlinecode{mkdir} of GNU Coreutils (default on GNU/Linux systems and installable in almost all Unix-like OSs). + Running the same command within a Conda environment that does not include GNU Coreutils on a macOS would crash. Important packages like GNU Coreutils are available in channels like conda-forge, but they are not the default. - Therefore, many users may not recognize this, and failing to account for it, will cause unexpected crashes. + Therefore, many users may not recognize this, and failing to account for it, will cause unexpected crashes when the project is run on a new system. \item Many major Conda packaging ``channels'' (for example the core Anaconda channel, or very popular conda-forge channel) do not include the C library, that a package was built with, as a dependency. They rely on the host operating system's C library. @@ -235,7 +241,7 @@ However, the resulting environment is not fully independent of the host operatin \item Conda does allow a package to depend on a special build of its prerequisites (specified by a checksum, fixing its version and the version of its dependencies). However, this is rarely practiced in the main Git repositories of channels like Anaconda and conda-forge: only the name of the high-level prerequisite packages is listed in a package's \inlinecode{meta.yaml} file, which is version-controlled. Therefore two builds of the package from the same Git repository will result in different tarballs (depending on what prerequisites were present at build time). - In the Conda tarball (that contains the binaries and is not under version control) \inlinecode{meta.yaml} does include the exact versions of most build-time dependencies. + In Conda's downloaded tarball (that contains the built binaries and is not under version control) the exact versions of most build-time dependencies are listed. However, because the different software of one project may have been built at different times, if they depend on different versions of a single software there will be a conflict and the tarball cannot be rebuilt, or the project cannot be run. \end{itemize} @@ -254,7 +260,7 @@ Because of such bootstrapping problems (for example how Spack needs Python to bu In conclusion for all package managers, there are two common issues regarding generic package managers that hinder their usage for high-level scientific projects: \begin{itemize} -\item {\bf\small Pre-compiled/binary downloads:} Most package managers (excluding Nix or its derivatives) only download the software in a binary (pre-compiled) format. +\item {\bf\small Pre-compiled/binary downloads:} Most package managers primarily download the software in a binary (pre-compiled) format. This allows users to download it very fast and almost instantaneously be able to run it. However, to provide for this, servers need to keep binary files for each build of the software on different operating systems (for example Conda needs to keep binaries for Windows, macOS and GNU/Linux operating systems). It is also necessary for them to store binaries for each build, which includes different versions of its dependencies. @@ -262,14 +268,15 @@ In conclusion for all package managers, there are two common issues regarding ge \item {\bf\small Adding high-level software:} Packaging new software is not trivial and needs a good level of knowledge/experience with that package manager. For example, each one has its own special syntax/standards/languages, with pre-defined variables that must already be known before someone can package new software for them. - However, in many research projects, the most high-level analysis software is written by the team that is doing the research, and they are its primary users, even when the software is distributed with free licenses on open repositories. - Although active package manager members are commonly very supportive in helping to package new software, many teams may not be able to make that extra effort/time investment. + However, in many research projects, the most high-level analysis software is written by the team that is doing the research, and they are its primary/only users, even when the software is distributed with free licenses on open repositories. + + Although active package manager members are commonly very supportive in helping to package new software, many teams may not be able to make that extra effort and time investment to package their most high-level (i.e., relevant) software in it. As a result, they manually install their high-level software in an uncontrolled, or non-standard way, thus jeopardizing the reproducibility of the whole work. This is another consequence of the detachment of the package manager from the project doing the analysis. \end{itemize} Addressing these issues has been the basic reason behind the proposed solution: based on the completeness criteria, instructions to download and build the packages are included within the actual science project, and no special/new syntax/language is used. -Software download, built and installation is done with the same language/syntax that researchers manage their research: using the shell (by default GNU Bash in Maneage) and Make (by default, GNU Make in Maneage). +Software download, built and installation is done with the same language/syntax that researchers manage their research: using the shell (by default GNU Bash in Maneage) for low-level steps and Make (by default, GNU Make in Maneage) for job management. @@ -302,12 +309,12 @@ With Git, changes in a project's contents are accurately identified by comparing When the user decides the changes are significant compared to the archived state, they can be ``committed'' into the history/repository. The commit involves copying the changed files into the repository and calculating a 40 character checksum/hash that is calculated from the files, an accompanying ``message'' (a narrative description of the purpose/goals of the changes), and the previous commit (thus creating a ``chain'' of commits that are strongly connected to each other like \ifdefined\separatesupplement -the figure on Git in the main body of the paper. +the figure on Git in the main body of the paper). \else Figure \ref{fig:branching}). \fi For example \inlinecode{f4953cc\-f1ca8a\-33616ad\-602ddf\-4cd189\-c2eff97b} is a commit identifier in the Git history of this project. -Commits are is commonly summarized by the checksum's first few characters, for example, \inlinecode{f4953cc}. +Commits are is commonly summarized by the checksum's first few characters, for example, \inlinecode{f4953cc} of the example above. With Git, making parallel ``branches'' (in the project's history) is very easy and its distributed nature greatly helps in the parallel development of a project by a team. The team can host the Git history on a web page and collaborate through that. @@ -321,20 +328,21 @@ For example, it is first necessary to download a dataset and do some preparation Each one of these is a logically independent step, which needs to be run before/after the others in a specific order. Hence job management is a critical component of a research project. -There are many tools for managing the sequence of jobs, below we review the most common ones that are also used the existing reproducibility solutions of Appendix \ref{appendix:existingsolutions}. +There are many tools for managing the sequence of jobs, below we review the most common ones that are also used the existing reproducibility solutions of Appendix \ref{appendix:existingsolutions} and Maneage. \subsubsection{Manual operation with narrative} \label{appendix:manual} -The most commonly used workflow system for many researchers is to run the commands, experiment on them, and keep the output when they are happy with it. -As an improvement, some researchers also keep a narrative description of what they ran. +The most commonly used workflow system for many researchers is to run the commands, experiment on them, and keep the output when they are happy with it (therefore loosing the actual command that produced it). +As an improvement, some researchers also keep a narrative description in a text file, and keep a copy of the command they ran. At least in our personal experience with colleagues, this method is still being heavily practiced by many researchers. -Given that many researchers do not get trained well in computational methods, this is not surprising and as discussed in +Given that many researchers do not get trained well in computational methods, this is not surprising. +As discussed in \ifdefined\separatesupplement the discussion section of the main paper, \else Section \ref{discussion}, \fi -we believe that improved literacy in computational methods is the single most important factor for the integrity/reproducibility of modern science. +based on this observation we believe that improved literacy in computational methods is the single most important factor for the integrity/reproducibility of modern science. \subsubsection{Scripts} \label{appendix:scripts} @@ -342,19 +350,20 @@ Scripts (in any language, for example GNU Bash, or Python) are the most common w They are primarily designed to execute each step sequentially (one after another), making them also very intuitive. However, as the series of operations become complex and large, managing the workflow in a script will become highly complex. -For example, if 90\% of a long project is already done and a researcher wants to add a followup step, a script will go through all the previous steps (which can take significant time). +For example, if 90\% of a long project is already done and a researcher wants to add a followup step, a script will go through all the previous steps every time it is run (which can take significant time). In other scenarios, when a small step in the middle of the analysis has to be changed, the full analysis needs to be re-run from the start. -Scripts have no concept of dependencies, forcing authors to ``temporarily'' comment parts that they do not want to be re-run (forgetting to un-comment such parts are the most common cause of frustration for the authors and others attempting to reproduce the result). +Scripts have no concept of dependencies, forcing authors to ``temporarily'' comment parts that they do not want to be re-run. +Therefore forgetting to un-comment them afterwards is the most common cause of frustration. -Such factors discourage experimentation, which is a critical component of the scientific method. -It is possible to manually add conditionals all over the script to add dependencies or only run certain steps at certain times, but they just make it harder to read and introduce many bugs themselves. +This discourages experimentation, which is a critical component of the scientific method. +It is possible to manually add conditionals all over the script, thus manually defining dependencies, or only run certain steps at certain times, but they just make it harder to read, add logical complexity and introduce many bugs themselves. Parallelization is another drawback of using scripts. While it is not impossible, because of the high-level nature of scripts, it is not trivial and parallelization can also be very inefficient or buggy. \subsubsection{Make} \label{appendix:make} Make was originally designed to address the problems mentioned above for scripts \citeappendix{feldman79}. -In particular, it addresses the context of managing the compilation of software programs that involve many source code files. +In particular, it was originally designed in the context of managing the compilation of software source code that are distributed in many files. With Make, the source files of a program that have not been changed are not recompiled. Moreover, when two source files do not depend on each other, and both need to be rebuilt, they can be built in parallel. This was found to greatly help in debugging software projects, and in speeding up test builds, giving Make a core place in software development over the last 40 years. @@ -373,27 +382,30 @@ Therefore all three components in a rule must be files on the running filesystem To decide which operation should be re-done when executed, Make compares the timestamp of the targets and prerequisites. When any of the prerequisite(s) is newer than a target, the recipe is re-run to re-build the target. When all the prerequisites are older than the target, that target does not need to be rebuilt. -The recipe can contain any number of commands, they should just all start with a \inlinecode{TAB}. -Going deeper into the syntax of Make is beyond the scope of this paper, but we recommend interested readers to consult the GNU Make manual for a nice introduction\footnote{\inlinecode{\url{http://www.gnu.org/software/make/manual/make.pdf}}}. +A recipe is just a bundle or shell commands that are executed if necessary. +Going deeper into the syntax of Make is beyond the scope of this paper, but we recommend interested readers to consult the GNU Make manual for a very good introduction\footnote{\inlinecode{\url{http://www.gnu.org/software/make/manual/make.pdf}}}. \subsubsection{Snakemake} -Snakemake is a Python-based workflow management system, inspired by GNU Make (which is the job organizer in Maneage), that is aimed at reproducible and scalable data analysis \citeappendix{koster12}\footnote{\inlinecode{\url{https://snakemake.readthedocs.io/en/stable}}}. +\label{appendix:snakemake} +Snakemake is a Python-based workflow management system, inspired by GNU Make (discussed above). +It is aimed at reproducible and scalable data analysis \citeappendix{koster12}\footnote{\inlinecode{\url{https://snakemake.readthedocs.io/en/stable}}}. It defines its own language to implement the ``rule'' concept of Make within Python. -Currently, it requires Python 3.5 (released in September 2015) and above, while Snakemake was originally introduced in 2012. -Hence it is not clear if older Snakemake source files can be executed today. -As reviewed in many tools here, this is a major longevity problem when using high-level tools as the skeleton of the workflow. Technically, calling command-line programs within Python is very slow, and using complex shell scripts in each step will involve a lot of quotations that make the code hard to read. +Currently, Snakemake requires Python 3.5 (released in September 2015) and above, while Snakemake was originally introduced in 2012. +Hence it is not clear if older Snakemake source files can be executed today. +As reviewed in many tools here, depending on high-level systems for low-level project components causes a major bootstrapping problem that reduces the longevity of a project. + \subsubsection{Bazel} Bazel\footnote{\inlinecode{\url{https://bazel.build}}} is a high-level job organizer that depends on Java and Python and is primarily tailored to software developers (with features like facilitating linking of libraries through its high-level constructs). \subsubsection{SCons} \label{appendix:scons} -Scons is a Python package for managing operations outside of Python (in contrast to CGAT-core, discussed below, which only organizes Python functions). +Scons\footnote{\inlinecode{\url{https://scons.org}}} is a Python package for managing operations outside of Python (in contrast to CGAT-core, discussed below, which only organizes Python functions). In many aspects it is similar to Make, for example, it is managed through a `SConstruct' file. Like a Makefile, SConstruct is also declarative: the running order is not necessarily the top-to-bottom order of the written operations within the file (unlike the imperative paradigm which is common in languages like C, Python, or FORTRAN). However, unlike Make, SCons does not use the file modification date to decide if it should be remade. -SCons keeps the MD5 hash of all the files (in a hidden binary file) to check if the contents have changed. +SCons keeps the MD5 hash of all the files in a hidden binary file and checks them to see if it is necessary to re-run. SCons thus attempts to work on a declarative file with an imperative language (Python). It also goes beyond raw job management and attempts to extract information from within the files (for example to identify the libraries that must be linked while compiling a program). @@ -410,7 +422,8 @@ This can also be problematic when a Python analysis library, may require a Pytho \subsubsection{CGAT-core} CGAT-Core is a Python package for managing workflows, see \citeappendix{cribbs19}. It wraps analysis steps in Python functions and uses Python decorators to track the dependencies between tasks. -It is used in papers like \citeappendix{jones19}, but as mentioned in \citeappendix{jones19} it is good for managing individual outputs (for example separate figures/tables in the paper, when they are fully created within Python). +It is used in papers like \citeappendix{jones19}. +However, as mentioned in \citeappendix{jones19} it is good for managing individual outputs (for example separate figures/tables in the paper, when they are fully created within Python). Because it is primarily designed for Python tasks, managing a full workflow (which includes many more components, written in other languages) is not trivial. Another drawback with this workflow manager is that Python is a very high-level language where future versions of the language may no longer be compatible with Python 3, that CGAT-core is implemented in (similar to how Python 2 programs are not compatible with Python 3). @@ -420,23 +433,24 @@ It is closely linked with GNU Guix and can even install the necessary software n Hence in the GWL paradigm, software installation and usage does not have to be separated. GWL has two high-level concepts called ``processes'' and ``workflows'' where the latter defines how multiple processes should be executed together. -In conclusion, shell scripts and Make are very common and extensively used by users of Unix-based OSs (which are most commonly used for computations). -They have also existed for several decades and are robust and mature. -Many researchers are also already familiar with them and have already used them. -As we see in this appendix, the list of necessary tools for the various stages of a research project (an independent environment, package managers, job organizers, analysis languages, writing formats, editors, etc) is already very large. -Each software has its own learning curve, which is a heavy burden for a natural or social scientist for example. -Most other workflow management tools are yet another language that have to be mastered. - -Furthermore, high-level and specific solutions will evolve very fast causing disruptions in the reproducible framework. -A good example is Popper \citeappendix{jimenez17} which initially organized its workflow through the HashiCorp configuration language (HCL) because it was the default in GitHub. -However, in September 2019, GitHub dropped HCL as its default configuration language, so Popper is now using its own custom YAML-based workflow language, see Appendix \ref{appendix:popper} for more on Popper. - \subsubsection{Nextflow (2013)} Nextflow\footnote{\inlinecode{\url{https://www.nextflow.io}}} \citeappendix{tommaso17} workflow language with a command-line interface that is written in Java. \subsubsection{Generic workflow specifications (CWL and WDL)} Due to the variety of custom workflows used in existing reproducibility solution (like those of Appendix \ref{appendix:existingsolutions}), some attempts have been made to define common workflow standards like the Common workflow language (CWL\footnote{\inlinecode{\url{https://www.commonwl.org}}}, with roots in Make, formatted in YAML or JSON) and Workflow Description Language (WDL\footnote{\inlinecode{\url{https://openwdl.org}}}, formatted in JSON). -These are primarily specifications/standards rather than software, so ideally translators can be written between the various workflow systems to make them more interoperable. +These are primarily specifications/standards rather than software. +With these standards, ideally, translators can be written between the various workflow systems to make them more interoperable. + +In conclusion, shell scripts and Make are very common and extensively used by users of Unix-based OSs (which are most commonly used for computations). +They have also existed for several decades and are robust and mature. +Many researchers that use heavy computations are also already familiar with them and have already used them already (to different levels). +As we demonstrated above in this appendix, the list of necessary tools for the various stages of a research project (an independent environment, package managers, job organizers, analysis languages, writing formats, editors, etc) is already very large. +Each software/tool/paradigm has its own learning curve, which is not easy for a natural or social scientist for example (who need to put their primary focus on their own scientific domain). +Most workflow management tools and the reproducible workflow solutions that depend on them are, yet another language/paradigm that has to be mastered by researchers and thus a heavy burden. + +Furthermore as shown above (and below) high-level tools will evolve very fast causing disruptions in the reproducible framework. +A good example is Popper \citeappendix{jimenez17} which initially organized its workflow through the HashiCorp configuration language (HCL) because it was the default in GitHub. +However, in September 2019, GitHub dropped HCL as its default configuration language, so Popper is now using its own custom YAML-based workflow language, see Appendix \ref{appendix:popper} for more on Popper. @@ -444,7 +458,7 @@ These are primarily specifications/standards rather than software, so ideally tr \subsection{Editing steps and viewing results} \label{appendix:editors} -In order to later reproduce a project, the analysis steps must be stored in files. +In order to reproduce a project, the analysis steps must be stored in files. For example Shell, Python, R scripts, Makefiles, Dockerfiles, or even the source files of compiled languages like C or FORTRAN. Given that a scientific project does not evolve linearly and many edits are needed as it evolves, it is important to be able to actively test the analysis steps while writing the project's source files. Here we review some common methods that are currently used. @@ -456,13 +470,16 @@ To solve this problem there are advanced text editors like GNU Emacs that allow However, editors that can execute or debug the source (like GNU Emacs), just run external programs for these jobs (for example GNU GCC, or GNU GDB), just as if those programs was called from outside the editor. With text editors, the final edited file is independent of the actual editor and can be further edited with another editor, or executed without it. -This is a very important feature that is not commonly present for other solutions mentioned below. +This is a very important feature and corresponds to the modularity criteria of this paper. +This type of modularity is not commonly present for other solutions mentioned below (the source can only be edited/run in a specific browser). Another very important advantage of advanced text editors like GNU Emacs or Vi(m) is that they can also be run without a graphic user interface, directly on the command-line. This feature is critical when working on remote systems, in particular high performance computing (HPC) facilities that do not provide a graphic user interface. Also, the commonly used minimalistic containers do not include a graphic user interface. +Hence by default all Maneage'd projects also build the simple GNU Nano plain-text editor as part of the project (to be able to edit the source directly within a minimal environment). +Maneage can also also optinally build GNU Emacs or Vim, but its up to the user to build them (same as their high-level science software). \subsubsection{Integrated Development Environments (IDEs)} -To facilitate the development of source files, IDEs add software building and running environments as well as debugging tools to a plain text editor. +To facilitate the development of source code in special programming languages, IDEs add software building and running environments as well as debugging tools to a plain text editor. Many IDEs have their own compilers and debuggers, hence source files that are maintained in IDEs are not necessarily usable/portable on other systems. Furthermore, they usually require a graphic user interface to run. In summary, IDEs are generally very specialized tools, for special projects and are not a good solution when portability (the ability to run on different systems and at different times) is required. @@ -470,10 +487,10 @@ In summary, IDEs are generally very specialized tools, for special projects and \subsubsection{Jupyter} \label{appendix:jupyter} Jupyter (initially IPython) \citeappendix{kluyver16} is an implementation of Literate Programming \citeappendix{knuth84}. +Jupyter's name is a combination of the three main languages it was designed for: Julia, Python, and R. The main user interface is a web-based ``notebook'' that contains blobs of executable code and narrative. Jupyter uses the custom built \inlinecode{.ipynb} format\footnote{\inlinecode{\url{https://nbformat.readthedocs.io/en/latest}}}. -Jupyter's name is a combination of the three main languages it was designed for: Julia, Python, and R. -The \inlinecode{.ipynb} format, is a simple, human-readable (can be opened in a plain-text editor) file, formatted in JavaScript Object Notation (JSON). +The \inlinecode{.ipynb} format, is a simple, human-readable format that can be opened in a plain-text editor) and formatted in JavaScript Object Notation (JSON). It contains various kinds of ``cells'', or blobs, that can contain narrative description, code, or multi-media visualizations (for example images/plots), that are all stored in one file. The cells can have any order, allowing the creation of a literal programming style graphical implementation, where narrative descriptions and executable patches of code can be intertwined. For example to have a paragraph of text about a patch of code, and run that patch immediately on the same page. @@ -486,7 +503,7 @@ It is possible to manually execute only one cell, but the previous/next cells th Integration of directional graph features (dependencies between the cells) into Jupyter has been discussed, but as of this publication, there is no plan to implement it (see Jupyter's GitHub issue 1175\footnote{\inlinecode{\url{https://github.com/jupyter/notebook/issues/1175}}}). The fact that the \inlinecode{.ipynb} format stores narrative text, code, and multi-media visualization of the outputs in one file, is another major hurdle and against the modularity criteria proposed here. -The files can easily become very large (in volume/bytes) and hard to read. +The files can easily become very large (in volume/bytes) and hard to read when the Jupyter web-interface is not accessible. Both are critical for scientific processing, especially the latter: when a web browser with proper JavaScript features is not available (can happen in a few years). This is further exacerbated by the fact that binary data (for example images) are not directly supported in JSON and have to be converted into a much less memory-efficient textual encoding. @@ -494,7 +511,7 @@ Finally, Jupyter has an extremely complex dependency graph: on a clean Debian 10 \citeappendix{hinsen15} reported such conflicts when building Jupyter into the Active Papers framework (see Appendix \ref{appendix:activepapers}). However, the dependencies above are only on the server-side. Since Jupyter is a web-based system, it requires many dependencies on the viewing/running browser also (for example special JavaScript or HTML5 features, which evolve very fast). -As discussed in Appendix \ref{appendix:highlevelinworkflow} having so many dependencies is a major caveat for any system regarding scientific/long-term reproducibility (as opposed to industrial/immediate reproducibility). +As discussed in Appendix \ref{appendix:highlevelinworkflow} having so many dependencies is a major caveat for any system regarding scientific/long-term reproducibility. In summary, Jupyter is most useful in manual, interactive, and graphical operations for temporary operations (for example educational tutorials). @@ -507,7 +524,7 @@ Currently, the most popular high-level data analysis language is Python. R is closely tracking it and has superseded Python in some fields, while Julia \citeappendix{bezanson17} is quickly gaining ground. These languages have themselves superseded previously popular languages for data analysis of the previous decades, for example, Java, Perl, or C++. All are part of the C-family programming languages. -In many cases, this means that the tools to use that language are written in C, which is the language of modern operating systems. +In many cases, this means that the language's execution environment are themselves written in C, which is the language of modern operating systems. Scientists, or data analysts, mostly use these higher-level languages. Therefore they are naturally drawn to also apply the higher-level languages for lower-level project management, or designing the various stages of their workflow. @@ -524,21 +541,23 @@ Some projects could not make this investment and their developers decided to sto The problems were not just limited to translation. Python 2 was still being actively used during the transition period (and is still being used by some, after its end-of-life). -Therefore, developers of packages used by others had to maintain (for example fix bugs in) both versions in one package. +Therefore, developers had to maintain (for example fix bugs in) both versions in one package. This is not particular to Python, a similar evolution occurred in Perl: in 2000 it was decided to improve Perl 5, but the proposed Perl 6 was incompatible with it. However, the Perl community decided not to abandon Perl 5, and Perl 6 was eventually defined as a new language that is now officially called ``Raku'' (\url{https://raku.org}). It is unreasonably optimistic to assume that high-level languages will not undergo similar incompatible evolutions in the (not too distant) future. -For software developers, this is not a problem at all: non-scientific software, and the general population's usage of them, has a similarly fast evolution. -Hence, it is rarely (if ever) necessary to look into codes that are more than a couple of years old. -However, in the sciences (which are commonly funded by public money) this is a major caveat for the longer-term usability of solutions that are designed in such high-level languages. +For industial software developers, this is not a major problem: non-scientific software, and the general population's usage of them, has a similarly fast evolution and shelf-life. +Hence, it is rarely (if ever) necessary to look into industrial/business codes that are more than a couple of years old. +However, in the sciences (which are commonly funded by public money) this is a major caveat for the longer-term usability of solutions. -In summary, in this section we are discussing the bootstrapping problem as regards scientific projects: the workflow/pipeline can reproduce the analysis and its dependencies, but the dependencies of the workflow itself can not be ignored. +In summary, in this section we are discussing the bootstrapping problem as regards scientific projects: the workflow/pipeline can reproduce the analysis and its dependencies. +However, the dependencies of the workflow itself should not be ignored. Beyond technical, low-level, problems for the developers mentioned above, this causes major problems for scientific project management as listed below: \subsubsection{Dependency hell} The evolution of high-level languages is extremely fast, even within one version. -For example, packages that are written in Python 3 often only work with a special interval of Python 3 versions (for example newer than Python 3.6). +For example, packages that are written in Python 3 often only work with a special interval of Python 3 versions. +For example Snakemake and Occam which can only be run on Python versions 3.4 and 3.5 or newer respectively, see Appendices \ref{appendix:snakemake} and \ref{appendix:occam}. This is not just limited to the core language, much faster changes occur in their higher-level libraries. For example version 1.9 of Numpy (Python's numerical analysis module) discontinued support for Numpy's predecessor (called Numeric), causing many problems for scientific users \citeappendix{hinsen15}. @@ -548,10 +567,11 @@ Acceptable version intervals between the dependencies will cause incompatibiliti Since a domain scientist does not always have the resources/knowledge to modify the conflicting part(s), many are forced to create complex environments with different versions of Python and pass the data between them (for example just to use the work of a previous PhD student in the team). This greatly increases the complexity of the project, even for the principal author. -A good reproducible workflow can account for these different versions. -However, when the actual workflow system (not the analysis software) is written in a high-level language this will cause a major problem. +A well-designed reproducible workflow like Maneage that has no dependencies beyond a C compiler in a Unix-like operating system can account for this. +However, when the actual workflow system (not the analysis software) is written in a high-level language like the examples above. -For example, merely installing the Python installer (\inlinecode{pip}) on a Debian system (with \inlinecode{apt install pip2} for Python 2 packages), required 32 other packages as dependencies. +Another relevant example of the dependency hell is mentioned here: +merely installing the Python installer (\inlinecode{pip}) on a Debian system (with \inlinecode{apt install pip2} for Python 2 packages), required 32 other packages as dependencies. \inlinecode{pip} is necessary to install Popper and Sciunit (Appendices \ref{appendix:popper} and \ref{appendix:sciunit}). As of this writing, the \inlinecode{pip3 install popper} and \inlinecode{pip2 install sciunit2} commands for installing each, required 17 and 26 Python modules as dependencies. It is impossible to run either of these solutions if there is a single conflict in this very complex dependency graph. @@ -563,8 +583,8 @@ Of course, this also applies to tools that these systems use, for example Conda This occurs primarily for domain scientists (for example astronomers, biologists, or social sciences). Once they have mastered one version of a language (mostly in the early stages of their career), they tend to ignore newer versions/languages. The inertia of programming languages is very strong. -This is natural because they have their own science field to focus on, and re-writing their high-level analysis toolkits (which they have curated over their career and is often only readable/usable by themselves) in newer languages every few years requires too much investment and time. +This is natural because they have their own science field to focus on, and re-writing their high-level analysis toolkits (which they have curated over their career and is often only readable/usable by themselves) in newer languages every few years is not practically possible. -When this investment is not possible, either the mentee has to use the mentor's old method (and miss out on all the new tools, which they need for the future job prospects), or the mentor has to avoid implementation details in discussions with the mentee because they do not share a common language. +When this investment is not possible, either the mentee has to use the mentor's old method (and miss out on all the newly fashionable tools that many are talking about), or the mentor has to avoid implementation details in discussions with the mentee because they do not share a common language. The authors of this paper have personal experiences in both mentor/mentee relational scenarios. This failure to communicate in the details is a very serious problem, leading to the loss of valuable inter-generational experience. |